Java Stream allMatch()

Java Stream allMatch() is a short-circuiting terminal operation that is used to check if all the elements in the stream satisfy the provided predicate.

1. Stream allMatch() Method

1.1. Syntax

boolean allMatch(Predicate<? super T> predicate)

Here predicate a non-interfering, stateless predicate to apply to all the elements of the stream.

The allMatch() method returns always a true or false, based on the result of the evaluation.

1.2. Description

• It is a short-circuiting terminal operation.
• It returns whether all elements of this stream match the provided predicate.
• May not evaluate the predicate on all elements if not necessary for determining the result. Method returns true if all stream elements match the given predicate, else method returns false.
• If the stream is empty then true is returned and the predicate is not evaluated.
• The difference between allMatch() and anyMatch() is that anyMatch() returns true if any of the elements in a stream matches the given predicate. When using allMatch(), all the elements must match the given predicate.

2. Stream allMatch() Examples

Let us look at a few examples of allMatch() menthod to understand its usage.

Example 1: Checking if Any Element Contains Numeric Characters

In the given example, none of the strings in the Stream contain any numeric character. The allMatch() checks this condition in all the strings and finally returns true.

Stream<String> stream = Stream.of("one", "two", "three", "four");

Predicate<String> containsDigit = s -> s.contains("\\d+") == false;

boolean match = stream.allMatch(containsDigit);

System.out.println(match);	

Program output.

true

Example 2: Stream.allMatch() with Multiple Conditions

To satisfy multiple conditions, create a composed predicate with two or more simple predicates.

In the given example, we have a list of Employee. We want to check if all the employees who are above the age of 50 – are earning above 40,000.

In the list, the employee "B" is earning below 40k and his age is above 50, so the result is false.

import java.util.ArrayList;
import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Stream;
import lombok.AllArgsConstructor;
import lombok.Data;
 
public class Main 
{
  public static void main(String[] args) 
  {
    Predicate<Employee> olderThan50 = e -> e.getAge() > 50;
    Predicate<Employee> earningMoreThan40K = e -> e.getSalary() > 40_000;
    Predicate<Employee> combinedCondition = olderThan50.and(earningMoreThan40K);
     
    boolean result = getEmployeeStream().allMatch(combinedCondition);
    System.out.println(result);
  }
   
  private static Stream<Employee> getEmployeeStream()
  {
    List<Employee> empList = new ArrayList<>();
    empList.add(new Employee(1, "A", 46, 30000));
    empList.add(new Employee(2, "B", 56, 30000));
    empList.add(new Employee(3, "C", 42, 50000));
    empList.add(new Employee(4, "D", 52, 50000));
    empList.add(new Employee(5, "E", 32, 80000));
    empList.add(new Employee(6, "F", 72, 80000));
     
    return empList.stream();
  }
}
 
@Data
@AllArgsConstructor
class Employee 
{
  private long id;
  private String name;
  private int age;
  private double salary;
}

Program output.

false

3. Conclusion

Stream.allMatch() method can be useful in certain cases where we need to run a check on all stream elements.

For example, we can use allMatch() on a stream of Employee objects to validate if all employees are above a certain age.

It is short-circuiting operation. A terminal operation is short-circuiting if, when presented with infinite input, it may terminate in finite time.

Happy Learning !!

Sourcecode on Github